ESTRO 2024 - Abstract Book

S3229

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Staff and public dose restriction requirements were established based on determined dose rates compared to UK legislation.

Results:

The FLASH survey revealed that specific areas of concern included the maze entrance, areas beyond the maze, and a plant room immediately above the maze.

Neutron dose rate (H*(10) µSv/h)

Photon dose rate (H*(10) µSv/h)

Total dose rate (H*(10) µSv/h)

Location

Biological experiment preparation room

41 ± 12.3

3.0 ± 0.3

44 ± 12.3

Toilet

22 ± 6.7

1.7 ± 0.2

24 ± 6.7

Store Room

15 ± 4.4

1.1 ± 0.2

16 ± 4.4

Maze entrance

180 ± 54

19 ± 1.7

200 ± 54

Corridor beyond maze (max)

18 ± 5.4

2.1 ± 0.3

20 ± 5.4

GR4 control room operator

15 ± 4.6

2.3 ± 0.3

18 ± 4.6

GR4 control room maze seat

74 ± 22

4.4 ± 0.5

78 ± 22

Plant room above maze

265 ± 80

14 ± 1.3

280 ± 80

Clinic rooms below maze

31 ± 9.4

1.8 ± 0.2

33 ± 9.4

Table 1 - FLASH radiation survey results

Monte-Carlo validation simulations using ICRU74 conversion factors matched measurements to within uncertainties (2 sigma) in the majority of key locations with the exception of the maze entrance, for which a model correction factor was determined. Conversion to effective dose using ICRP 116 factors to determine effective dose showed a two-fold reduction in dose in the maze entrance compared to using ICRP 74 factors, and all other locations sampled were also found to be significantly lower (Figure 1), demonstrating the value of using Monte-Carlo simulations in this context.